Ungrounded systems ?

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John120/240

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In another thread ungrounded systems was brought up. I think I remember hearing about a keyless with a A19 lamp (one for each phase) being used for Ground detection. So do you just have these at the Main Gear or is it practical to locate Ground detectors at sub panels ?

Which state of the lamps indicates a fault ?
 
When one phase goes to ground, the lamps for that phase go out, the other two phases get brighter.
Almost all those set-up I have seen were at the main distribution. Feeders can be switched off to isolate the feeder with the problem. From there you work your down to the circuit with the ground.
 
You can put a ground detector of this nature anywhere you like. I have only seen them at the main panel, however, and that was during my active Navy days. We had to push a button to light the ground detection lights.
 
John120/240 said:
In another thread ungrounded systems was brought up. I think I remember hearing about a keyless with a A19 lamp (one for each phase) being used for Ground detection. So do you just have these at the Main Gear or is it practical to locate Ground detectors at sub panels ?

Which state of the lamps indicates a fault ?
Click to expand...


Perfect person to ask. Just encountered one again. There are several ways to do it. One is 3 A19 sockets connected across each phase and then have each shell wire connected to the ground buss. Under normal conditions both bulbs glow dimly. If one goes out and the other 2 are bright that indicates a full ground fault.


However, such a set requires 240 volt bulbs, and on a 480 volt system 480 volt bulbs would be needed but I don't know of any A-19 bulbs with that voltage.

To solve the issue transformers (small ones about 50VA) are added across the sockets to step it down to 120 volts. That allows regular bulbs to be used on any voltage.

Here is the transformer method: http://www.expertsmind.com/CMSImages/2391_Ground Detector1.png

http://etc.usf.edu/clipart/36200/36226/cutout_gd_36226_sm.gif
 
charlie b said:
You can put a ground detector of this nature anywhere you like. I have only seen them at the main panel, however, and that was during my active Navy days. We had to push a button to light the ground detection lights.
Click to expand...
Another version I've seen was lamps connected through a "push-to-test" button... to make sure when lamp went out it didn't just burn out. Don't want to be chasing ghosts... :happyno:
 
mbrooke said:
Perfect person to ask. Just encountered one again. There are several ways to do it. One is 3 A19 sockets connected across each phase and then have each shell wire connected to the ground buss. Under normal conditions both bulbs glow dimly. If one goes out and the other 2 are bright that indicates a full ground fault.


However, such a set requires 240 volt bulbs, and on a 480 volt system 480 volt bulbs would be needed but I don't know of any A-19 bulbs with that voltage.

To solve the issue transformers (small ones about 50VA) are added across the sockets to step it down to 120 volts. That allows regular bulbs to be used on any voltage.

Here is the transformer method: http://www.expertsmind.com/CMSImages/2391_Ground Detector1.png

http://etc.usf.edu/clipart/36200/36226/cutout_gd_36226_sm.gif
Click to expand...
A lot of the ones around here used two 240 volt lamps in series for each phase on a 480 volt system.
 
mbrooke said:
Explain. :? Not saying your wrong just Ive always thought a screw shell had to be on a grounded conductor.
Click to expand...

Just the way the code sections are worded. It looks like they intentionally left the door open to say a 240 volt lamp supplied by two hots. :)

410.50 Polarization of Luminaires. Luminaires shall be
wired so that the screw shells of lampholders are connected
to the same luminaire or circuit conductor or terminal.
The grounded conductor, where connected to a screw
shell lampholder, shall be connected to the screw shell.
Click to expand...


410.90 Screw Shell Type. Lampholders of the screw shell
type shall be installed for use as lampholders only. Where
supplied by a circuit having a grounded conductor, the
grounded conductor shall be connected to the screw shell.
Click to expand...
 
The first code section would not appear to apply to indicator lamps as opposed to luminaires.
But if you consider all three (6?) bulbs to be part of one luminaire, there is no way to satisfy it in a three phase system without a neutral. Which would just mean that you could not use screw type lampholders.
:)

Tapatalk!
 
GoldDigger said:
The first code section would not appear to apply to indicator lamps as opposed to luminaires.
But if you consider all three (6?) bulbs to be part of one luminaire, there is no way to satisfy it in a three phase system without a neutral. Which would just mean that you could not use screw type lampholders.
:)

Tapatalk!
Click to expand...

The only ground fault indicators I have seen using screw shell lamps where not luminaires, they were simply six lampholders of the screwshell type monted on an enclosure.
 
iwire said:
Just the way the code sections are worded. It looks like they intentionally left the door open to say a 240 volt lamp supplied by two hots. :)
Click to expand...


The last section seems to allow it.:eek: So that means you could technically have a keyless socket connected to 240 and use a 240 volt bulb anywhere??
 
mbrooke said:
The last section seems to allow it.:eek: So that means you could technically have a keyless socket connected to 240 and use a 240 volt bulb anywhere??
Click to expand...

Yes, IMHO.
And on a side note, the first sentence of 410.90 seems to explicitly prohibit use of screw-in receptacle adapters.

Tapatalk!
 
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